There are today numerous medicament delivery devices on the market where the main intention is to use them for self-administration of medicament. The patient or user should thus be able to use the device, whereby the device should be easy and intuitive to use for a wide range of patients from children to elderly as well as persons with reduced dexterity of the hands.
In many instances it is an advantage that different doses may be set individually by the user. This could for example be that a user should take different doses during a medication period or that the same device could be used for different persons requiring different doses, such as children and adults requiring different quantities of medicament.
It could also be an advantage that the force member, such as a spring, acting on a medicament container in order to expel a dose, is tensioned when a dose is set. In this way the device does not have to be stored in a highly tensioned state as often is the case with devices using spiral compression springs. Thus, the risk of damage to the devices due to creeping effects in the materials of the device is greatly reduced.
With this type of function some devices have been utilizing torsion springs as strip spiral springs, or clock springs, that are wound in a spiral having a central passage in which a hub is placed. Document WO 2008/155144 discloses a medicament delivery device arranged with a strip clock spring. The spring is arranged transversal in relation to the longitudinal direction of the device and is tensioned by turning a knob at the distal end of the device. The use of a torsion spring in this fashion means that the distal end of the device becomes rather bulky with a much larger diameter than the proximal part of the device. Further the placement of a dose setting knob is limited to the distal end of the device.
For some applications this design is not optimal and it would be advantageous to have another design and position of the dose setting knob or wheel, which may be more intuitive. Documents WO 9856436 and WO9810813 disclose a medicament delivery device provided with a dose setting wheel having an axis of rotation generally perpendicular to the longitudinal direction of the device. The intention with this design is to provide a dose setting mechanism allowing larger digits or numbers to be displayed as well as a larger dose setting wheel which in total facilitates the dose setting for persons with impaired sight and/or dexterity in their hands. However, when a dose is to be delivered, the mechanism is completely manual and the user has to press a dose delivery button on the distal end of the device. The manual actuation of the dose delivery is however not optimal for persons with weak hands, and in particular if the medicament is of higher viscosity than water, which requires higher forces to push the medicament through a medicament delivery member such as an injection needle. There is thus room for improvement of the state of the art medicament delivery devices.